Class II Springs to the Archwire

 

Drs. Miller, Tieu, and Flores-Mir's article titled "Incisor inclination changes produced

by two compliance-free Class II correction protocols for the treatment of mild to

moderate Class II malocclusions" is in the online version of the Angle Orthodontist.

It is based on Dr. Bob Miller's clinical study.

He compared 36 Class II patients treated in one phase with Forsus to the archwire

in a full edgewise appliance to 38 similar Class II patients treated in two phases

with Xbow followed by a full edgewise appliance. The Forsus to the archwire group

was finished in an average of 30.2 months (between records). The Xbow group was finished

in an average of 24.2 months (between records), which included a 4 to 6 month rest period

to allow for relapse. The two phase Xbow patients were completed 6 months faster on

average than the one phase Forsus to the archwire patients (time between records). 

The Forsus to the archwire group had full braces for an average of 26.75 months. The

Xbow group had full braces for an average of 16.68 months, or 10 fewer months.

There was no significant difference in the lower incisor to mandibular plane angle

between the two groups. The Xbow patients ended up with lower incisors at an average

of 100 degrees to mandibular plane which is considered a reasonable compromise for

non-extraction Class II compensation.

Editor's note: Longer treatment time with Forsus to the archwire is due to dealing

with the spring side effects late in treatment such as posterior openbite and

buccal flaring of the upper molars. The greater the correction the greater the

side effects and the longer it takes to deal with them.

There is no buccal flaring of the upper molars with Xbow.

Much of the posterior openbite and proclination of the lower incisors rebound

before full braces are placed.

 


The side-effects of Forsus on the archwire are especially problematic when the spring is used unilaterally late in treatment.

The unilateral posterior openbite and anterior canting requires prolonged treatment with good elasitc cooperation to recover.

We do not see the anterior canting when the spring is used unilaterally on a Xbow.

The fact that the first bicuspids are already Class I after Xbow therapy reduces the time in phase two braces

and the need for side-effect correction with elastics.

 

I use the same principles when using the Forsus device with a full edgewise appliance as I do with Xbow. 

Use the 22mm Direct Pushrod distal to the lower first bicuspid instead of the canine, if possible. 

This keeps the Forsus device more compact and  moves it distal to the anterior curvature of the arch,

preventing the need for rod adjustments. It also keeps the spring distal to the Obicularis Oris muscle, preventing sores.

The only difference is you cannot fully compress the spring with an edgewise appliance if you use a bracket as the anterior stop. 

If you do be prepared to rebond the bracket.  Don't forget to steel tie the first bicuspids. 

Reactivate the springs with crimpable stops on the rods or use longer rods.

Dr. Bob Miller taught us to hook up the pushrod using an Alastic KX module to activate the spring but at the same time remove

the force from the canine or first bicuspid bracket.  This also negates the need to cinch the distal end of the arch wire.  

Place the springs and pushrods as you would normally but don't close the loop yet.  Make the pushrod adjustments

leaving 1mm of play in the spring, remove the pushrod, pre-stretch a KX-1 module, place the KX module on the pushrod,

place the pushrod on the archwire, close the pushrod loop,  hook the KX module to the first molar hook using floss

and a floss threader over the second bicuspid bracket and down between the second bicuspid and first molar,

then place the pushrod in the spring.  This completely activates the spring without debonding the canine or first bicuspid bracket. 

If we place the 22 mm or 25 mm pushrod distal to the first bicuspid we use a KX-1 module. 

We also use a KX-1 module distal to the canine in a bicuspid extraction case. 

Alastic KX-1 module placed with floss threader

Alastic KX-1 module and lingual tuck-in pushrod adjustment on 25mm rod

Alastic KX-1 module hook-up distal to canine (severe Class II, patient decided against mandibular advancement surgery after preparation)

Alastic KX-1 Module hook-up distal to first bicuspid

 

Alastic KX-1 Module hook-up distal to canine (bicuspid extraction) with a 22 mm pushrod.

Spring Sleeve available from Comfort Solutions

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